>whatever is going on in france

Two things:

-a design choice: the fee also pays for rest areas every 15-20 km, for both cars and trucks

-an unchosen situation: France is right in the middle of Europe and sees half* the of the population of Northern European countries driving through it to go on vacation in the Southern ones every Easter, Summer and Autumn vacations (and to the alpine ski stations in Winter).

*Kidding, but only slightly